非地转湿Q矢量在川北大暴雨过程分析中的应用

Ageostrophic Wet Q-Vector Analysis and Its Application to a Heavy Rainstorm in North Sichuan Basin

利用常规高空和地面实测资料,对2005-07-18～19出现在四川盆地北部的区域性大暴雨天气过程的环流特征进行了分析;运用非地转湿Q矢量理论进行了动力诊断分析。结果表明,在副高阻挡的形势下,高低空切变线、地面冷锋和偏南低空急流的共同作用造成了此次暴雨天气过程;暴雨区位于湿Q矢量次级环流上升区附近,在其东西方向和南北方向上存在明显的次级环流圈;700hPa湿Q矢量散度负值中心附近及其西部和北部之间的辐合区是强降水出现的区域,随着暴雨系统的发展,其散度辐合区与雨区对应得越好。

Using the routine observation data,the circulation feature of a regional heavy rain process in North Sichuan Basin on 18～19 July 2005 was analyzed.A dynamic diagnosis was made by using the ageostrophic wet Q-vector theory.The results showed as follows.This heavy rain process attributed to the influencing of upper and lower shear lines,the surface cold front and the southerly low-level jet streams blocked by Northwest Pacific subtropical high together.The heavy rain occurred in the area of updraft triggered by the wet Q-vector.There was obvious secondary circulation around the updraft.The convergence center of the wet Q-vector and the convergence area between the north and west of the center on 700 hPa were the areas where the torrential rain occurred.Along with the development of heavy rain system the convergence area could correspond to the heavy precipitation area better.